The changing ecology of tropical forests

The threat to tropical forests is often gauged in terms of deforestation rates and the total area remaining. Recently, however, there has been a growing realization that forest can appear intact on a satellite image yet be biologically degraded or vulnerable to degradation. The array of direct threats to humid tropical forest biodiversity, in addition to deforestation, includes: selective extraction of plants; selective extraction of animals; biological invasion; fragmentation; climate change; changing atmospheric composition; and increasing tree turnover rates. The threats are linked to one another by a poorly understood network of causality and feedback effects. Moreover, their potential impacts on forest biodiversity are hard to assess because each threat is as likely to precipitate indirect effects as direct effects, and because several threats are likely to interact synergistically with one another. In spite of the uncertainties, it is clear that the biological health of tropical forests can become seriously degraded as a result of these threats, and it is unlikely that any tropical forest will escape significant ecological changes. Some groups of plants and animals are likely to benefit at the expense of others. Species diversity is expected to decline as a consequence of the changes in forest ecology. In the 21st century scientists and conservationists will be increasingly challenged to monitor, understand, prevent and head off these threats.     

The biogeochemical heterogeneity of tropical forests

Tropical forests are renowned for their biological diversity, but also harbor variable combinations of soil age, chemistry and susceptibility to erosion or tectonic uplift. Here we contend that the combined effects of this biotic and abiotic diversity promote exceptional biogeochemical heterogeneity at multiple scales. At local levels, high plant diversity creates variation in chemical and structural traits that affect plant production, decomposition and nutrient cycling. At regional levels, myriad combinations of soil age, soil chemistry and landscape dynamics create variation and uncertainty in limiting nutrients that do not exist at higher latitudes. The effects of such heterogeneity are not well captured in large-scale estimates of tropical ecosystem function, but we suggest new developments in remote sensing can help bridge the gap.     

The boreal forests of north-eastern Eurasia

The distribution, diversity and structure of boreal forests of monsoon Asia are reviewed. The boreal zone is circumscribed by the isotherms of 15°C and 45°C of Kira's Warmth Index (WI) and includes the territory of the Amur basin, the seashores of the Sea of Okhotsk, Kamchatka, Sakhalin and the Kuril islands. Boreal forests also occur on the mountains of Hokkaido, Honshu, Korea and NE China. The oceanic sectors of the boreal zone are composed mainly of birch forests, the marine sectors of spruce-fir forests and the continental sectors of larch and pine forests. The upper limit of the boreal forests ascends from the lowest level in the North to ca. 1500 m a.s.l. in the South of the zone, and reaches above 2500 m in the mountains of the temperate zone. In the boreal zone the secondary forests are common. They form after fires and cutting. Volcanism is an essential factor in the forest dynamics in the oceanic part of the region. It is suggested that as a result of global warming one may expect a strong alteration in vegetation pattern, especially in the northern and mountain areas.Paper presented at the International Symposium on Global Change Impacts on Terrestrial Ecosystems in Monsoon Asia (TEMA) Waseda University, Tokyo, 4–6 September 1993.     

Jordan Raff

Jordan Raff is a Cancer Research UK funded group leader at the Wellcome/CR-UK Gurdon Institute in Cambridge, England. He obtained his PhD from the Department of Biochemistry at Imperial College, London, and he worked as a Post-doctoral fellow at the Department of Biophysics and Biochemistry, University of California, San Francisco. He is currently a Director of the Company of Biologists, and on the committee of the British Society of Cell Biology. He has studied centrosomes and cell division in fruit flies throughout his scientific career.     

Horseflies of Jordan

The horsefly (Diptera: Tabanidae) fauna of Jordan consists of 21 species belonging to seven genera. The present study adds 17 new records to this little-known group of haematophagous insects. Most of the new records were collected from several localities within the Jordan Valley. These new records are Chrysops flavipes Meigen, Atylotus farinosus (Szilády), Dasyrhamphis umbrinus (Meigen), Haematopota coronata Austen, Hybomitra decora (Loew), Hybomitra mendica (Villeneuve), Tabanus accensus Austen, T. albifacies Loew, T. bifarius Loew, T. darimonti Leclercq, T. laetetinctus Becker, T. leleani Austen, T. pallidipes Austen, T. regularis Jaennicke, T. rupinae Austen, T. sufis Jaennicke and Therioplectes tunicatus (Szilády). Tabanus albifacies and T. sufis were the most common species collected by hand nets (19.85% and 17.73%, respectively) and D. umbrinus, Haematopota minuscula Austen, and Haematopota coronata were the least common species (0.12% for each). Zoogeographical analysis of the recorded species showed that 12 species are of Mediterranean origin, four are of Afrotropical origin, two of European origin and at least three species can be considered as endemic to the Middle East.     

Spectres of Jordan

Abstract

Despite retiring from the National Basketball Association (NBA) in 2003, the iconic basketball player Michael Jordan continues to inform popular understandings of race and racial difference. Jordan could thus be considered a raced spectre (Derrida 1994): a fantastically racialized figure derived from, and cast in the mould of, the contingencies of an earlier moment in American history, who nonetheless informs the racial politics and experience of the present. In examining Jordan's enduring influence on contemporary America's implicitly raced neoliberal formation, this discussion involves: a re-envisioning of the raced neoliberal politics implicit within, and mobilized by, Jordan's commodified identity; an illustration of how the institutionalization of racial logics derived from Jordan's idealized raced subjectivity have come to inform the racially regressive management and governance of the NBA; an exhumation of how the very form of Jordan's enduring phantasm has been accommodated to shifting, and increasingly interwoven, commercial and racial forces; and an examination of the contemporaneous manifestations and influences of the Jordan spectre.     

The chromosomes of Arixenia esau Jordan (Dermaptera)

The parasitic insect Arixenia esau, a highly aberrant member of the order Dermaptera, shows n = 30 and has an XY sex determining mechanism. This karyotype is compared with those of the earwigs (Forficulina) and of Hemimerus bouvieri, a member of another aberrant parasitic suborder of the Dermaptera.Supported by Public Health Service Grant GM-07212 from the Division of General Medical Sciences, U.S. National Institutes of Health and by a grant from the Australian Research Grants Committee.     

The carbon budget of the Spanish forests

A model for the calculation of anthropogenic CO₂ emissions from perturbed forests (extraordinary emissions) is described. Timber production as well as wildfire statistics are used, and relevant physicochemical parameters are derived from the literature, to calculate the annual amounts of perturbed biomass and extraordinary emissions to the atmosphere from the Spanish forests — including soils — in the years 1960–1990; these emissions increased from 5.3 10⁶ t (metric tons) of carbon in 1970 to 10.6 10⁶ t C in 1990. A sensitivity analysis of the results has been performed to identify the most critical parameters. Contributions of observed timber growth and natural vegetal detritus and soil organic matter to the net forest carbon flux have been estimated to calculate the carbon budget in the Spanish forests between 1966 and 1974, which represents a net gain of carbon, ranging from 9.2 to 18 millions t. Finally, the methods used to calculate biospheric carbon balance and their results are compared and discussed.     

The ecogeographical differentiation of Amazonian inundation forests

Due to the considerable annual fluctuations of water level of the Amazonian rivers, their river banks are fringed with periodically flooded forests of vast extension. The biota of these communities are adapted to annual inundations that can last for more than half a year. Water chemistry is most important for the floristic differentiation of these flooded forests. White water rivers, which carry a rich load of suspended material originating from the erosion of the Andes, have a floristic composition related to that of the noninundatable Amazonian forest. Clear water and black water rivers, which originate in the Amazon Basin or its adjacent crystalline shields, are nutrient-poor and more or less acidic; their flora is related to that of peculiar woodland and savannah vegetation on oligotrophic white sand. The distribution patterns of floodplain species of nutrient-poor waters point to a centre of diversity in the Upper Rio Negro region, and another one in the Guayana lowland. These coincide with diversity centres for species of non-flooded habitats. Hence it seems unlikely that species diversity is directly influenced by pluviosity. The flooded forests have developed biotic interactions with the fish fauna of the Amazon Basin, which are vital for their continued existence. It is assumed that the origin of these habitats, their biota and their interactions dates back long into the Tertiary.     

The puzzling ecology of African Marantaceae forests

Marantaceae forests are tropical rainforests characterized by a continuous understory layer of perennial giant herbs and a near absence of tree regeneration. Although widespread in West-Central Africa, Marantaceae forests have rarely been considered in the international literature. Yet, they pose key challenges and opportunities for theoretical ecology that transcend the borders of the continent. Specifically, we ask in this review whether open Marantaceae forests and dense closed-canopy forests can be considered as one of the few documented examples of alternative stable states in tropical forests. First, we introduce the different ecological factors that have been posited to drive Marantaceae forests (climate, soil, historical and recent anthropogenic pressures, herbivores) and develop the different hypotheses that have been suggested to explain how Marantaceae forests establish in relation with other vegetation types (understory invasion, early succession after disturbance, and intermediate successional stage). Then, we review the underlying ecological mechanisms that can explain the stability of Marantaceae forests in the long term (tree recruitment inhibition, promotion of and resilience to fire, adaptive reproduction, maintenance by megaherbivores). Although some uncertainties remain and call for further empirical and theoretical research, we found converging evidence that Marantaceae forests are associated with an ecological succession that has been deflected or arrested. If verified, Marantaceae forests may provide a useful model to understand critical transitions in forest ecosystems, which is of particular relevance to achieve sustainable forest management and mitigate global climate change.     

The seroepidemiology of Hepatitis A virus in Amman, Jordan

Hepatitis A virus (HAV) has emerged as an important public health problem in many countries of the Middle East region and Jordan is no exception. From January 1991 to December 2001, a total of 1015 patients were diagnosed at Al-Battikhi Medical Laboratories. Samples were collected at seventeen private laboratories distributed throughout areas of the Governorate of Amman (capital of Jordan). A significant variation (P=0.03) was obtained between number of HAV cases and year. Seasonal variation in HAV cases was seen throughout the study period with maximal rates in the spring and summer months (P<0.001). The highest incidence rate (9.6/100,000 population) was detected in the year 1993 and the lowest incidence rate (1.1/100,000 population) was found in the year 2001. There was a significant difference (P<0.0001) between number of HAV cases and age group. The highest number of cases 166 (16.4%) was reported for age group 5-14 years and the lowest number of cases 18 (0.02%). Male to female ratio was 1.25: 1. There was no significant sex variation (P=0.28). A significant variation (P=0.006) was observed between number of HAV cases and districts. The present results suggested a link between the age groups, year, month and occurrence of HAV infection. Male to female ratio indicates no significant sex variation.     

The importance of nutrient pulses in tropical forests

Recent research shows that nutrient fluxes are often pulsed In tropical forests, and that pulsed versus gradual inputs have different effects on the fates of nutrients in the ecosystem. Synchrony of nutrient mineralization with plant uptake can lower competition between microbes and plants for limiting nutrients while maintaining tight nutrient cycling, whereas asynchrony can lead to losses of nutrients from the system. Thus, nutrient pulses may play a critical role in maintaining productivity in tropical forests with tight nutrient cycling.